1. The Field of the Invention
The present invention relates to the field of network communications. More specifically, the present invention relates to the real-time communication of multimedia information over heterogeneous networks.
2. The Related Art
Multimedia information includes information that is efficiently interpretable by one or more of the five human senses, but mostly by the human senses of sight and hearing. For example, video information is interpreted by the senses of sight and hearing. Audio information is interpreted by the sense of hearing. Some user interfaces such as Braille displays present information for interpretation by the sense of touch. However, with the advancement of appropriate user interfaces, multimedia information may also include taste and smell information as well.
Often, multimedia information is time-sensitive and should be rendered at the same speed that the information is sampled within some minimal jitter tolerances. This type of multimedia presentation will often be referred herein as “real-time”. For efficient real-time delivery of multimedia data, the networks between the multimedia source and the multimedia sink should be abstracted so that the networks as a whole function as a constant delay network.
FIG. 1 illustrates a conventional network 100 for delivering multimedia data in real-time. A multimedia source 101 transmits multimedia packets 104 over a constant delay network 103 to a multimedia sink 102. Of course, there is always some variance in the delay, however small, introduced by any network. However, a “constant delay” network is a network in which the delay variance introduced by the network is below the minimal jitter tolerances required to support real-time presentation of the multimedia data.
As illustrated in FIG. 1, the constant delay network 103 may include a number of different network types that follow different standards. Nevertheless, in order to support real-time multimedia data delivery, each component network must support the abstraction of the networks as a whole into the constant delay network. There are generally two classifications of networks that support this kind of abstraction into an amalgamated constant delay network.
One such classification is constant delay networks. Thus, for example, the constant delay network 103 of FIG. 1 includes a component constant delay network 105. Constant delay networks receive multimedia data from a point on the network at a certain receive rate, and deliver the multimedia data to another point on the network at the same rate so that there is a relatively constant delay. A second such classification is variable delay networks that have a common notion of time.
It is possible even in such variable delay networks to emulate a constant delay network if the network supports a common notion of time across the network. For example, the IEEE 1394 serial bus is not inherently a constant delay network. However, the IEEE 1394 serial bus does support a common notion of time. The IEC 61883-x standard uses the common notion of time present in the IEEE 1394 serial bus to have the IEEE 1394 serial bus emulate a constant delay network to within the jitter tolerances required under the MPEG-2 standard.
Referring to FIG. 1, the constant delay network 103 also may include a variable delay network 106. If a series of one or more contiguous variable delay networks is interposed between the multimedia source 101 and the multimedia sink 104, the series of variable delay networks may emulate a constant delay network if the string of variable delay networks shares a common notion or reckoning of time.
Thus, conventional methods allow for the real-time delivery of multimedia data over a network that includes both constant delay networks and variable delay networks that have a common notion of time. However, there is a third classification of networks that is not compatible with being a component network in an amalgamated constant delay network under conventional standards. That third classification is a variable delay network that does not have a common notion of time.
Under conventional technology, real-time communication of multimedia data is not possible if one or more of the networks that must be traversed are variable delay networks that do not have a common notion of time. Accordingly, there exists no conventional infrastructure for seamlessly communicating multimedia over heterogeneous networks in real-time since those heterogeneous networks may include one or more variable delay networks that contain no common time reference across the network. Establishing such an infrastructure would allow for better access to multimedia content regardless of the heterogenic nature of the networks that intervene between the multimedia source and the multimedia sink.